1. Field of the Invention
The present invention relates to monolithically integrated audio amplifiers.
2. Description of the Prior Art
An ever increasing output power is requested from battery operated integrated audio amplifiers (car radios, portable radios and tape players, etc.). This has made popular integrated amplifiers capable of operating in a bridge configuration and, therefore theoretically capable of delivering to a loudspeaker of the sound reproduction system a peak voltage equal to twice the supply (battery) voltage. On the other hand, in case of somewhat lesser quality appliances, a single-ended configuration having an output dynamic equal to the supply voltage is still widely used. Such a configuration offers a reduced power dissipation and requires a lesser number of single amplification stages.
For obvious reasons, manufacturers of such appliances favor the use of integrated circuits requiring as few as possible external components and, on the other hand, having a small size package.
Also for easily comprehensible reasons and to minimize inventories, manufacturers of these apparatuses welcome the possibility of stocking a single integrated device capable of being connected to an external circuit and to operate correctly in a bridge configuration as well as in a single-ended or stereo configuration.
There are at present few commercially available integrated devices capable of permitting the connection in a bridge or in a stereo configuration of two amplifiers integrated monolithically on a single chip. These known devices utilize a rather cumbersome package having a large number of pins which permit, through the connection to an external circuit, obtaining either a bridge configuration or a stereo configuration of the two integrated amplifiers. Of course, integrated devices in small size, seven pin packages are available for either a bridge application or a stereo application, but not for both.